tbh i don’t know anything in the horse world that is “reasonably price”. however, the best inexpensive(ish) one i know is the novle outfitters ringside pack (it’s on smartpak.com) and i think it’s between $80 - $90. if youre in the splurge mood, i’d highly recommend either the maelort backpacks ($200-$220) or the samshield iconpack ($250)!!
dover just came out with one for like $80 i believe
I really like baseball backpacks from sporting good stores because they have a place for a helmet and you can put whips where the bats are meant to go!
I have the Ariat riding back pack and I love it I got it for I think $100 and I bought it from dover saddlery.
If you mean backpack as like a school bag I would just go and get a cheap one from somewhere like big w or target Kmart or Walmart if you live in America, cause they'll do good but